Maneuvering Mobile Robots

ABSTRACT

A method of maneuvering a robot includes driving the robot across a surface and turning the robot by shifting a center of mass of the robot toward a turn direction, thereby leaning the robot into the turning direction. The robot includes an inverted pendulum body, a counter-balance body disposed on the inverted pendulum body and configured to move relative to the inverted pendulum body, at least one leg prismatically coupled to the inverted pendulum body, and a drive wheel rotatably coupled to the at least one leg. The inverted pendulum body has first and second end portions and defines a forward drive direction. The method also includes turning the robot by at least one of moving the counter-balance body relative to the inverted pendulum body or altering a height of the at least one leg with respect to the surface.

TECHNICAL FIELD

This disclosure relates to mobile robots and methods of maneuvering mobile robots across surfaces.

BACKGROUND

Robots currently perform tasks in various working environments, such as factories, storage facilities, office buildings, and hospitals. Moreover, robots are sometimes designed with large stationary or moveable bases that allow the robot to maintain an upright position while performing tasks that involve lifting and handling heavy objects without tipping over. The large bases, however, tend to be heavy, unwieldy, and cumbersome, severely limiting mobility and being inappropriate for use in areas with tight footprints. While other robots with smaller and lighter bases or mobility platforms are more maneuverable than the robots with large bases, they are typically not practical for carrying heavy objects due to instabilities resulting from shifts in center of mass and changes in momentum as the objects are picked up and put down.

SUMMARY

A method of maneuvering a robot includes driving the robot across a surface and turning the robot by shifting a center of mass of the robot toward a turn direction, thereby leaning the robot into the turning direction. The robot includes an inverted pendulum body, a counter-balance body disposed on the inverted pendulum body and configured to move relative to the inverted pendulum body, at least one leg prismatically coupled to the inverted pendulum body, and a drive wheel rotatably coupled to the at least one leg. The inverted pendulum body has first and second end portions and defines a forward drive direction. The method also includes turning the robot by at least one of moving the counter-balance body relative to the inverted pendulum body or altering a height of the at least one leg with respect to the surface.

Implementations of the disclosure may include one or more of the following optional features. In some implementations, shifting the center of mass of the robot toward the turning direction causes the drive wheel of the at least one leg to lean into the turning direction. The at least one leg may include a right leg having first and second ends and a left leg having first and second ends. The first end of the right leg is prismatically coupled to the second end portion of the inverted pendulum body. The right leg has a right drive wheel rotatably coupled to the second end of the right leg. The first end of the left leg is prismatically coupled to the second end portion of the inverted pendulum body. The left leg has a left drive wheel rotatably coupled to the second end of the left leg, wherein altering the height of the at least one leg includes altering the height of at least one of the right leg or the left leg of the robot with respect to the surface, causing the right and left drive wheels to lean into the turning direction.

In some examples, turning the robot further includes at least one of turning the robot at a turn parameter that satisfies a threshold turn parameter for a turn or leaning the robot at a roll angle that satisfies a threshold roll angle of the robot. In this example, the roll angle is measured between the surface and a line extending from a point of contact between the wheel of the at least one leg and the surface and the center of mass of the robot. The turn parameter may include a turn rate of change and the threshold turn parameter may include a threshold turn rate of change. Optionally, the turn parameter may include a yaw angle and the threshold turn parameter may include a threshold yaw angle.

In some configurations, the robot further includes at least one arm disposed on the inverted pendulum body and configured to move relative to the inverted pendulum body, wherein turning the robot further includes moving the at least one arm relative to the inverted pendulum body to assist movement of the center of mass of the robot. The at least one arm may be rotatably coupled to one of the first end portion of the inverted pendulum body or the second end portion of the inverted pendulum body. Moreover, the counter-balance body may be rotatably coupled to one of the first end portion of the inverted pendulum body or the second end portion of the inverted pendulum body.

Another aspect of the disclosure provides a robot including an inverted pendulum body having first and second end portions, a counter-balance body disposed on the inverted pendulum body and configured to move relative to the inverted pendulum body, at least one leg having first and second ends and a variable length between the first and second ends, and a drive wheel rotatably coupled to the second end of the at least one leg. The at least one leg is prismatically coupled to the second end portion of the inverted pendulum body. The robot further includes a controller in communication with the counter-balance body, the at least one leg, and the drive wheel. The controller is configured to perform operations that include: driving, by the drive wheel, the robot across a surface; and turning the robot by shifting a center of mass of the robot toward a turning direction, thereby leaning the robot into the turning direction. The controller shifts the center of mass of the robot by at least one of moving the counter-balance body relative to the inverted pendulum body or altering the length of the at least one leg.

This aspect may include one or more of the following optional features. In some implementations, shifting the center of mass of the robot toward the turning direction causes the drive wheel of the at least one leg to lean into the turning direction. The at least one leg may include a right leg having first and second ends and a left leg having first and second ends. The first end of the right leg is prismatically coupled to the second end portion of the inverted pendulum body. The right leg has a right drive wheel rotatably coupled to the second end of the right leg. The first end of the left leg is prismatically coupled to the second end portion of the inverted pendulum body. The left leg has a left drive wheel rotatably coupled to the second end of the left leg, wherein altering the height of the at least one leg includes altering the height of at least one of the right leg or the left leg of the robot with respect to the surface, causing the right and left drive wheels to lean into the turning direction.

In some examples, turning the robot further includes at least one of turning the robot at a turn parameter that satisfies a threshold turn parameter for a turn or leaning the robot at a roll angle that satisfies a threshold roll angle of the robot. In this example, the roll angle is measured between the surface and a line extending from a point of contact between the wheel of the at least one leg and the surface and the center of mass of the robot. The turn parameter may include a turn rate of change and the threshold turn parameter may include a threshold turn rate of change. Optionally, the turn parameter may include a yaw angle and the threshold turn parameter may include a threshold yaw angle.

In some configurations, the robot further includes at least one arm disposed on the inverted pendulum body and configured to move relative to the inverted pendulum body, wherein turning the robot further includes moving the at least one arm relative to the inverted pendulum body to assist movement of the center of mass of the robot. The at least one arm may be rotatably coupled to one of the first end portion of the inverted pendulum body or the second end portion of the inverted pendulum body. Moreover, the counter-balance body may be rotatably coupled to one of the first end portion of the inverted pendulum body or the second end portion of the inverted pendulum body.

The details of one or more implementations of the disclosure are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is schematic view of an example robot.

FIGS. 1B and 1C are schematic views of the robot of FIG. 1A showing a counter-balance body moving relative to an inverted pendulum body of the robot.

FIGS. 1D and 1E are schematic vies showing an example robot having two appendages disposed on an inverted pendulum body.

FIG. 1F is a schematic view of an example robot driving along a path having straight portions and curved portions.

FIG. 1G is a schematic view of an example robot having a single articulated arm and leaning into a turning direction while the robot executes a turning maneuver.

FIG. 1H is a schematic view of an example robot having two articulated arms and leaning into a turning direction while the robot executes a turning maneuver.

FIG. 1I is a schematic view of the robot of FIG. 1F turning at a yaw angle that satisfies a threshold yaw angle for a turn.

FIG. 1J is detailed view of left and right drive wheels of the robot of FIG. 1F while leaning into a turning direction while the robot executes a turning maneuver.

FIG. 2 is a schematic view of an example robot.

FIG. 3 is a schematic view of an example robot.

FIG. 4 is a schematic view of an example arrangement of operations for a method of operating a robot.

FIG. 5 is a schematic view of an example computing device that may be used to implement the systems and methods described herein.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Maneuverable robots are susceptible to losing balance due to instabilities resulting from shifts in center of masses and changes in moment while performing tasks that involve lifting and handling heavy objects. Centrifugal forces may also cause a center of pressure to move outside a center of support, thereby contributing to robot instability. The robots are even more prone to losing balance while executing turning maneuvers due to center of mass and/or center of pressure shifts away from a turning direction. For instance, depending upon a velocity of a robot, turning at a turn rate-of-change that is too fast and/or at a turning angle (e.g., yaw angle) that is too large, may result in the robot tipping over due to a center of mass shift away from the turning direction. Implementations herein are directed toward driving the robot across a surface and turning the robot by shifting a center of mass of the robot toward a turning direction to lean the robot into the turning direction. The robot may shift the center of mass toward the turning direction by at least one of moving a counter-balance body of the robot relative to an inverted pendulum body or altering a height of at least one leg of the robot with respect to the surface. The altering of the height of the last least one leg may allow for a drive wheel rotatably coupled to the at least one leg to bank into the turn to enhance the turn.

Referring to FIGS. 1A-1E, in some implementations, a robot 100, 100 a includes an inverted pendulum body (IPB) 200, a counter-balance body 300 disposed on the IPB 200, at least one leg 400 having a first end 410 coupled to the IPB 200 and a second end 420, and a drive wheel 500 rotatably coupled to the second end 420 of the at least one leg 400. The robot 100 has a vertical gravitational axis V_(g) (FIGS. 1B and 1C) along a direction of gravity, and a center of mass CM, which is a point where the robot 100 has a zero sum distribution of mass. The robot 100 further has a pose P based on the CM relative to the vertical gravitational axis V_(g) to define a particular attitude or stance assumed by the robot 100. The attitude of the robot 100 can be defined by an orientation or an angular position of an object in space.

The IPB 200 has first and second end portions 210, 220 and may be interchangeably referred to as a torso 200 for the robot 100. For instance, the IPB 200 may define a length between a first end 212 associated with the first end portion 210 and a second end 222 associated with the second end portion 220. In some examples, a point of delineation separating the first and second end portions 210, 220 is at a midpoint between the first end 212 and the second end 222, so that the first end portion 210 encompasses 50-percent of the length of the IPB 200 and the second end portion 220 encompasses the remaining 50-percent of the length of the IPB 200. In other examples, the point of delineation separating the first and second end portions 210, 220 of the IPB 200 is closer to one of the first end 212 or the second end 222 so that one of the first end portion 210 or the second end portion 220 extends along a larger portion of the length of the IPB 200 than the other one of the first end portion 210 or the second end portion 220. For instance, the first end portion 210 extending from the first end 212 may encompass 90-, 80-, 70-, 60-, 40-, 30-, 20-, 10-percent of the length of the IPB 200 while the second end portion 220 extending from the second end 222 may encompass the remaining 10-, 20-, 30-, 60-, 70-, 80-, 90-percent of the length of the IPB 200.

In some implementations, the counter-balance body 300 is disposed on the first end portion 210 of the IPB 200 and configured to move relative to the IPB 200. The counter-balance body 300 may be interchangeably referred to as a tail 300. A back joint bk, 350 may rotatably couple the counter-balance body 300 to the first end portion 210 of the IPB 200 to allow the counter-balance body 300 to rotate relative to the IPB 200. In the example shown, the back joint bk, 350 supports the counter-balance body 300 to allow the counter-balance body 300 to move/pitch around a lateral axis (y-axis) that extends perpendicular to the gravitational vertical axis V_(g) and a fore-aft axis (x-axis) of the robot 100. The fore-aft axis (x-axis) may denote a present direction of travel by the robot 100.

Referring to FIG. 1B, the counter-balance body 300 has a longitudinal axis L_(CBB) extending from the back joint bk, 350 and is configured to pivot at the back joint bk, 350 to move/pitch around the lateral axis (y-axis) relative to the IPB 200 (in both the clockwise and counter-clockwise directions relative to the view shown in FIG. 1B). Accordingly, the back joint bk, 350 may be referred to as a pitch joint. The pose P of the robot 100 may be defined at least in part by a rotational angle θ_(CBB) of the counter-balance body 300 relative to the vertical gravitational axis V_(g). Moreover, the counter-balance body 300 may generate/impart a moment M_(CBB) (rotational force) at the back joint bk, 350 based on the rotational angle θ_(CBB) of the counter-balance body 300 relative to the vertical gravitational axis V_(g). Thus, movement by the counter-balance body 300 relative to the IPB 200 alters the pose P of the robot 100 by moving the CM of the robot 100 relative to the vertical gravitational axis V_(g). A rotational actuator 352 (e.g., a tail actuator) may be positioned at or near the back joint bk, 350 for controlling movement by the counter-balance body 300 (e.g., tail) about the lateral axis (y-axis). The rotational actuator 352 may include an electric motor, electro-hydraulic servo, piezo-electric actuator, solenoid actuator, pneumatic actuator, or other actuator technology suitable for accurately effecting movement of the counter-balance body 300 relative to the IPB 200.

The rotational movement by the counter-balance body 300 relative to the IPB 200 alters the pose P of the robot 100 for balancing and maintaining the robot 100 in an upright position. For instance, similar to rotation by a flywheel in a conventional inverted pendulum flywheel, rotation by the counter-balance body 300 relative to the gravitational vertical axis V_(g) generates/imparts the moment M_(CBB) at the back joint bk, 350 to alter the pose P of the robot 100. By moving the counter-balance body 300 relative to the IPB 200 to alter the pose P of the robot 100, the CM of the robot 100 moves relative to the gravitational vertical axis Vg to balance and maintain the robot 100 in the upright position in scenarios when the robot 100 is moving and/or carrying a load. However, by contrast to the flywheel portion in the conventional inverted pendulum flywheel that has a mass centered at the moment point, the counter-balance body 300 includes a corresponding mass that is offset from the moment M_(CBB) imparted at the back joint bk, 350. In some configurations, a gyroscope disposed at the back joint bk, 350 could be used in lieu of the counter-balance body 300 to spin and impart the moment M_(CBB) (rotational force) for balancing and maintaining the robot 100 in the upright position.

Referring to FIG. 1C, the counter-balance body 300 may rotate (e.g., pitch) about the back joint bk, 350 in both the clockwise and counter-clockwise directions (e.g., about the y-axis in the “pitch direction” relative to the view shown in FIG. 1C) to create an oscillating (e.g., wagging) movement. For example, the counter-balance body 300 may move/pitch about the lateral axis (y-axis) in a first direction (e.g., counter-clockwise direction) from a first position (solid lines) associated with longitudinal axis L_(CBB1), having a first rotational angle θ_(CBB1) relative to the vertical gravitation axis V_(g), to a second position (dashed lines) associated with longitudinal axis L_(CBB2), having a second rotational angle θ_(CBB2) relative to the vertical gravitation axis V_(g). Movement by the counter-balance body 300 relative to IPB 200 from the first position to the second position causes the CM of the robot 100 to shift and lower toward the ground surface 12.

The counter-balance body 300 may also move/pitch about the lateral axis (y-axis) in an opposite second direction (e.g., clockwise direction) from the second position (dashed lines) back to the first position or another position either before or beyond the first position. Movement by the counter-balance body 300 relative to the IPB 200 in the second direction away from the second position (dashed lines) causes the CM of the robot 100 to shift and raise away from the ground surface 12. Thus, increasing the rotational angle θ_(CBB) of the counter-balance body 300 relative to the vertical gravitational axis V_(g) may cause the CM of the robot 100 to lower toward the ground surface 12, while decreasing the rotational angle θ_(CBB) of the counter-balance body 300 relative to the vertical gravitational axis V_(g) may cause the CM of the robot 100 to raise away from the ground surface 12 and/or shift forward or backward relative to the point of contact between the drive wheels 500 and the ground surface 12. In some examples, the longitudinal axis L_(CBB) of the counter-balance body 300 is coincident with the vertical gravitational axis V_(g). The counter-balance body 300 may oscillate between movements in the first and second directions to create the wagging movement. The rotational velocity of the counter-balance body 300 when moving relative to the IPB 200 may be constant or changing (accelerating or decelerating) depending upon how quickly the pose P of the robot 100 needs to be altered for dynamically balancing the robot 100.

The first position (solid lines) associated with L_(CBB1) and the second position (dashed lines) associated with L_(CBB1) of the counter-balance body 300 of FIG. 1C are depicted as exemplary positions only, and are not intended to represent a complete range of motion of the counter-balance body 300 relative to the IPB 200. For instance, in other examples, the counter-balance body 300 may move/pitch around the lateral axis (y-axis) in the first direction (e.g., counter-clockwise direction) to positions having rotational angles θ_(CBB) greater than the second rotational angle θ_(CBB2) associated with the second position (dashed lines) and/or in the second direction (e.g., clockwise direction) to positions having rotational angles θ_(CBB) less than the first rotational angle θ_(CBB1) associated with the first position (solid lines). Moreover, the counter-balance body 300 may move/pitch around the lateral axis (y-axis) relative to the IPB 200 at any position between the first position (solid lines) and the second position (dashed lines) shown in FIG. 1C.

Referring back to FIGS. 1A and 1B, the at least one leg 400 includes a right leg 400 a and a left leg 400 b. The right leg 400 a includes a corresponding first end 410, 410 a rotatably coupled to the second end portion 220 of the IPB 200 and a corresponding second end 420, 420 a rotatably coupled to a corresponding right drive wheel 500, 500 a. A right hip joint 412 may rotatably couple the first end 410 a of the right leg 400 a to the second end portion 220 of the IPB 200 to allow at least a portion of the right leg 400 a to move/pitch around the lateral axis (y-axis) relative to the IPB 200. A leg actuator 413 associated with the hip joint 412 may cause an upper portion 401, 401 a of the right leg 400 a to move/pitch around the lateral axis (y-axis) relative to the IPB 200. In some configurations, the right leg 400 a includes the corresponding upper portion 401, 401 a and a corresponding lower portion 402, 402 a. The upper portion 401 a may extend from the hip joint 412 at the first end 410 a to a corresponding knee joint 414 and the lower portion 402 a may extend from the knee joint 414 to the second end 420 a.

The right leg 400 a may include a corresponding right ankle joint 422, 422 a configured to rotatably couple the right drive wheel 500 a to the second end 420 a of the right leg 400 a. Here, the right ankle joint 422 a may be associated with a wheel axle coupled for common rotation with the right drive wheel 500 a and extending substantially parallel to the lateral axis (y-axis). The right drive wheel 500 a may include a corresponding torque actuator (drive motor) 510, 510 a configured to apply a corresponding axle torque T_(a) (FIG. 1B) for rotating the right drive wheel 500 a about the ankle joint 422 a to move the right drive wheel 500 a across the ground surface 12 along the fore-aft axis (x-axis). For instance, the axle torque T_(a) may cause the right drive wheel 500 a to rotate in a first direction for moving the robot 100 in a forward direction along the fore-aft axis (x-axis) and/or cause the right drive wheel 500 a to rotate in an opposite second direction for moving the robot 100 in a rearward direction along the fore-aft axis (x-axis).

The left leg 400 b similarly includes a corresponding first end 410, 410 b rotatably coupled to the second portion 220 of the IPB 200 and a corresponding second end 420, 420 b rotatably coupled to a corresponding left drive wheel 500, 500 b. A corresponding hip joint 412 may rotatably couple the first end 410 b of the left leg 400 b to the second end portion 220 of the IPB 200 to allow at least a portion of the left leg 400 b to move/pitch around the lateral axis (y-axis) relative to the IPB 200. A corresponding leg actuator 413 associated with the left hip joint 412 may cause a corresponding upper portion 401, 401 b of the left leg 400 b to move/pitch around the lateral axis (y-axis) relative to the IPB 200. As with the right leg 400 a, the left leg 400 b may include the corresponding upper portion 401, 401 b and a corresponding lower portion 402, 402 b. The upper portion 401 b may extend from the hip joint 412 at the first end 410 b to a corresponding knee joint 414 and the lower portion 402 b may extend from the knee joint 414 to the second end 420 b.

The left leg 400 b may include a corresponding left ankle joint 422, 422 b configured to rotatably couple the left drive wheel 500 b to the second end 420 b of the left leg 400 b. Here, the left ankle joint 422 b may be associated with a wheel axle coupled for common rotation with the left drive wheel 500 b and extending substantially parallel to the lateral axis (y-axis). As with the right drive wheel 500 a, the left drive wheel 500 b may include a corresponding torque actuator (e.g., drive motor) 510 b configured to apply a corresponding axle torque T_(a) for rotating the left drive wheel 500 b about the ankle joint 422 b to move the left drive wheel 500 b across the ground surface 12 along the fore-aft axis (x-axis). For instance, the axle torque T_(a) may cause the left drive wheel 500 b to rotate in the first direction for moving the robot 100 in the forward direction along the fore-aft axis (x-axis) and/or cause the left drive wheel 500 b to rotate in the opposite second direction for moving the robot 100 in the rearward direction along the fore-aft axis (x-axis).

The corresponding axle torques T_(a) applied to each of the drive wheels 500 a, 500 b may vary to maneuver the robot 100 across the ground surface 12. For instance, an axle torque Tax applied to the right drive wheel 500 a that is greater than an axle torque T_(aL) applied to the left drive wheel 500 b may cause the robot 100 to turn to the left, while applying a greater axle torque T_(a) to the left drive wheel 500 b than to the right drive wheel 500 a may cause the robot 100 to turn to the right. Similarly, applying substantially the same magnitude of axle torque T_(a) to each of the drive wheels 500 a, 500 b may cause the robot 100 to move substantially straight across the ground surface 12 in either the forward or reverse directions. The magnitude of axle torque T_(a) applied to each of the drive wheels 500 a, 500 b also controls velocity of the robot 100 along the fore-aft axis (x-axis). Optionally, the drive wheels 500 a, 500 b may rotate in opposite directions to allow the robot 100 to change orientation by swiveling on the ground surface 12. Thus, each axle torque T_(a) may be applied to the corresponding drive wheel 500 independent of the axle torque T_(a) (if any) applied to the other drive wheel 500.

FIG. 1B shows the right ankle joint 422 a (e.g., wheel axle) rotatably coupling the right drive wheel 500 a to the second end 420 a of the right leg 400 a and exerting an axle force F_(a). The left ankle joint 422 b similarly exerts a corresponding axle force F_(a) (not shown). The axle forces F_(a) may assist in adjusting the pose P of the robot 100 and/or be controlled for balancing the robot 100. The axle force F_(a) is generated based on a magnitude of horizontal force F_(x) exerted on the corresponding ankle joint 422 along the fore-aft axis (x-axis), a magnitude of vertical force F_(z) exerted on the corresponding ankle joint 422 along a vertical axis (z-axis), and the magnitude of axle torque T_(a) applied by the corresponding torque actuator 510 to the correspond corresponding wheel 500.

In some implementations, each leg 400 has a variable length extending between the first and second ends 410, 420 of the corresponding leg 400. For instance, the lower portion 402 of each leg 400 may rotate relative to the corresponding upper portion 401 about the knee joint 414 to enable the leg 400 to retract and expand. Referring to FIG. 1B, rotation by the lower portion 402 about the knee joint 414 relative to the upper portion 401 in the counter-clockwise direction may cause the leg 400 to retract. At the same time, the upper portion 401 may rotate about the hip joint 412 relative to the IPB 200 in the clockwise direction to cause the leg 400 to retract. Similarly, rotation by the lower portion 402 about the knee joint 414 relative to the upper portion 401 in the clockwise direction and/or rotation by the upper portion 401 about the hip joint 412 relative to the IPB 200 in the counter-clockwise direction may cause the leg 400 to expand. As used herein, retracting the length of the leg 400 may cause a height of the corresponding leg 400 with respect to the ground surface 12 to reduce while expanding the length of the leg 400 may cause the height of the corresponding leg 400 with respect to the ground surface 12to increase. In some examples, the height of the leg 400 is defined as a distance along the vertical axis (z-axis) between the ground surface 12 (or the corresponding ankle joint 422) supporting the robot 100 and the corresponding knee joint 414. In other examples, the height of the leg 400 is defined as a distance along the vertical axis (z-axis) between the ground surface 12 (or the corresponding ankle joint 422) and the corresponding hip joint 412 rotatably coupling the corresponding first end 410 of the leg 400 to the second end portion 220 of the IPB 200.

In some implementations, retracting the length of both legs 400 causes an overall height of the robot 100 to decrease while expanding the length of both legs 400 causes the overall height of the robot 100 to increase. For instance, the robot 100 may need to lower, for example by crouching, to clear obstacles such as, without limitation, doorways, overhangs, light fixtures, or ceilings. It may also be desirable to lower the robot 100 to shift the CM downward to increase stability in certain scenarios. On the other hand, an increase to the overall height of the robot 100 may be required to reach or place a target object on a shelf Altering the height of the robot 100 simultaneously alters the pose P, and may cause substantive shifts in the CM of the robot 100 that require actuation of the counter-balance body 300 to move relative to the IPB 200 to maintain balance of the robot 100. The heights of the legs 400 may be dynamically controlled to target heights to assist with turning maneuvers as the robot 100 traverses along the ground surface 12. For instance, dynamically adjusting the height of each leg 400 independently from one another may allow the robot 100 to lean and bank into turns, thereby enhancing maneuverability of the robot 100 while traversing across the ground surface 12.

Referring back to FIG. 1A, retracting and expanding the length of each leg 400 may be controlled via a corresponding belt drive actuator 415 configured to drive a belt 417 coupled for common rotation with the corresponding knee joint 414. For instance, each leg 400 may include a corresponding belt drive actuator 415 disposed at or near the corresponding hip joint 412 and the corresponding belt 417 may have a first end coupled to the actuator 415 and a second end coupled to the knee joint 414. Here, the belt drive actuator 415 may rotate the corresponding upper portion 401 relative to the IPB 200 and drive the belt 417 in one direction to prismatically extend/expand the length of the leg 400 by causing the corresponding lower portion 402 to rotate about the knee joint 414 relative to the upper portion 401 in the clockwise direction (relative to the view of FIG. 1A). On the other hand, the belt drive actuator 415 may drive the belt 417 in the opposite direction to prismatically retract the length of the leg 400 by causing the corresponding lower portion 402 to rotate about the knee joint 414 relative to the upper portion 401 in the counter-clockwise direction (relative to the view of FIG. 1A). The belt 417 may include a continuous loop extending along the upper portion 402 of each leg 400 or may include terminal ends each connected to a respective one of the belt drive actuator 415 or the knee joint 414. The belt drive actuator 415 may include a ball-screw type actuator. In some examples, the belt drive actuator 415 and belt 417 employs a 2:1 belt coupling so that the lower portion 402 rotates about the knee joint 414 relative to the upper portion 401 at twice the angle of the rotation of the upper portion 401 about the hip joint 415, thereby causing the second end 420 of the leg 400 to move on a straight line equivalent to a linear rail. Optionally, instead of a two-link leg (e.g., upper and lower portions 401, 402), the at least one leg 400 may include a single link that prismatically extends/retracts linearly such that the second end 420 of the leg 400 prismatically moves away/toward the IPB 200 along a linear rail. Accordingly, the at least one leg 400 includes a prismatic leg having the first end 410 prismatically coupled to the second end portion 220 of the IPB 200 and configured to provide prismatic extension/retraction via actuation of the belt drive actuator 415 to drive the belt 417 in corresponding first or second directions. In other configurations, the knee joint 414 may employ a corresponding rotational actuator for rotating the lower portion 402 relative to the upper portion 401 in lieu of the belt 417 driven by the belt drive actuator 415 disposed at or near the hip joint 412.

In some implementations, the robot 100 further includes one or more appendages, such as an articulated arm 600 disposed on the IPB 200 and configured to move relative to the IPB 200. The articulated arm 600 may have five-degrees of freedom. Moreover, the articulated arm 600 may be interchangeably referred to as a manipulator arm, a manipulator head, or simply an appendage. While FIGS. 1A-1E show the articulated arm 600 disposed on the second end portion 220 of the IPB 200, the articulated arm 600 may be disposed on the first end portion 210 of the IPB 200 in other configurations. The articulated arm 600 extends between a proximal first end 610 and a distal second end 620. Referring to FIG. 1B, the first end 610 connects to the IPB 200 at a first articulated arm joint J₀ 650. The first articulated arm joint J₀ 650 may be disposed between the left and right hip joints 412 to center the articulated arm 600 between the left and right sides of the IPB 200. In some examples, the first articulated arm joint J₀ 650 rotatably couples the proximal first end 610 of the articulated arm 600 to the IPB 200 to enable the manipulator arm 600 to rotate relative to the IPB 200. For instance, the articulated arm 600 may move/pitch about the lateral axis (y-axis) relative to the IPB 200. A rotational actuator 652 (e.g., manipulator head actuator) may be positioned at or near the first articulated arm joint J₀ 650 for rotating the articulated arm 600 (e.g., manipulator head) about the lateral axis (y-axis). The rotational actuator 652 may include an electric motor, electro-hydraulic servo, piezo-electric actuator, solenoid actuator, pneumatic actuator, or other actuator technology suitable for accurately effecting movement of the articulated arm 600.

In some scenarios, the articulated arm 600 rotates at the first articulated arm joint J₀ 650 about the lateral axis (y-axis) relative to the IPB 200 in the direction of gravity (e.g., in the clockwise direction relative to the view of FIG. 1B) to lower the CM of the robot 100. The robot 100 may lower the CM closer to the ground surface while executing turning maneuvers. The counter-balance body 300 may also simultaneously rotate about the lateral axis (y-axis) relative to the IPB 200 in the direction of gravity (e.g., in the counter-clockwise direction relative to the view of FIG. 1B) to assist in lowering the CM of the robot 100. Here, the articulated arm 600 and the counter-balance body 300 may cancel out any shifting in the CM of the robot 100 in the forward or rearward direction along the fore-aft axis (x-axis), while still effectuating the CM of the robot 100 shift downward closer to the ground surface 12.

An end effector 700 may be disposed on the distal second end 620 of the manipulator arm 600. The end effector 700 may include one or more actuators 702 (grippers) that may be configured to grip and manipulate a target object. Additionally or alternatively, the end effector 700 may employ a vacuum device and/or one or more suction cups 704 (FIG. 1A) configured to apply suction for gripping and holding a target object when the end effector 700 is positioned on the target object. FIG. 1B shows the end effector 700 exerting a corresponding end effector force F_(ee). The manipulator arm 600 and/or the end effector 700 may include perception sensors for identifying objects in relation to the robot 100.

The articulated arm 600 may include two or more portions. In the examples shown in FIGS. 1A-1C, the articulated arm 600 includes a first portion 601, a second portion 602, and a third portion 603. The first portion 601 may extend between the proximal first end 610 connected to the IPB 200 via the first articulated arm joint J₀ 650 and a second articulated arm joint J₁ 660. The second portion 602 may extend between the second articulated arm joint J₁ 660 and a third articulated arm joint J₂ 670. The third portion 603 may extend between the third articulated arm joint J₂ 670 and the distal second end 620 of the articulated arm 600 that connects to the end effector 700. As with the first articulated arm joint J₀ 650, the second and third articulated arm joints J₁ 660, J₂ 670 may each be associated with a corresponding actuator 662, 672 configured to move each portion 602, 603 relative to one another and relative to the IPB 200. For instance, the rotational actuator 652 associated with the first articulated arm joint J₀ 650 may cause the first portion 601 of the articulated arm 600 to move/pitch about the lateral axis (y-axis) relative to the IPB 200. As the second and third portions 602, 603 of the articulated arm 600 are connected to the first portion 601 via the second and third articulated arm joints J₁ 660, J₂ 670, the rotation by the first portion 601 about the lateral axis (y-axis) at the first articulated arm joint J₀ 650 may also cause the second and third portions 602, 603 to simultaneously move relative to the IPB 200.

Similarly, the rotational actuator 662 associated with the second articulated arm joint J₁ 660 may cause the second portion 602 of the articulated arm 600 to move/pitch about the lateral axis (y-axis) relative to both the IPB 200 and the first portion 601 of the articulated arm 600. Moreover, the rotational actuator 672 associated with the third articulated arm joint J₂ 670 may cause the third portion 603 of the articulated arm 600 to move/pitch about the lateral axis (y-axis) relative to the IPB 200 and the first and second portions 601, 602 of the articulated arm 600. The actuators 652, 662, 672 may be controlled independently of one another to move the corresponding portions 601, 602, 603 alone or in concert for positioning the end effector 700 on a target object and/or altering the pose P of the robot 100.

In some configurations, the counter-balance body 300 corresponds to a first counter-balance body 300 disposed on the first end portion 210 of the IPB 200 and the articulated arm 600 corresponds to a second counter-balance body 600 disposed on the second end portion 210 of the IPB 200. Similar to the first counter-balance body 300 discussed above, the articulated arm 600 may be configured to move relative to the IPB 200 for altering the pose P of the robot 100 by moving the CM of the robot 100 relative to the vertical gravitational axis V_(g). For instance, the articulated arm 600 may generate/impart a moment M_(AA) (rotational force) (FIG. 1B) at the first articulated arm joint J₀ based on a rotational angle of the articulated arm 600 relative to the vertical gravitational axis V_(g). Thus, the articulated arm 600 may move relative to the IPB 200 to alter the pose P of the robot 100 by moving the CM of the robot 100 relative to the vertical gravitational axis V_(g). In some configurations, a gyroscope could be disposed at the first articulated arm joint J₀ to impart the moment M_(AA) (rotational force) for maintaining balance of the robot 100 in the upright position.

Referring to FIGS. 1D and 1E, in some implementations, the robot 100 includes left and right appendages (e.g., two articulated arms) 600 a, 600 b each disposed on the IPB 200 and configured to move relative to the IPB 200. The appendages 600 a, 600 b may be disposed on the first end portion 210 of the IPB 200 or the second end portion 220 of the IPB 200. As with the single articulated arm 600, each appendage 600 a, 600 b extends between a respective proximal first end 610 and a respective distal second end 620, and the first end 610 connects to the IPB 200 at a corresponding first articulated arm joint J₀ 650. Here, each first articulated arm joint J₀ 650 may be disposed on an opposite side of the IPB 200. Each appendage 600 a, 600 b may also include the one or more respective portions 601, 602, 603 connected by respective articulated arm joints J₁ 660, J₂ 670 as discussed above with reference to the single articulated arm 600 of FIGS. 1A-1C. Accordingly, each appendage 600 a, 600 b may be controlled to operate in substantially the same manner as the single articulated arm 600.

FIG. 1D shows the appendages 600 a, 600 b each having the corresponding first and second portions 601, 602 extending substantially parallel to one another and away from the IPB 200, while the corresponding third portion 603 extends substantially perpendicular to the first and second portions 601, 602 to point the corresponding distal second end 620 downward toward the ground surface 12. Here, the position of the appendages 600 a, 600 b may align the end effectors 700 and associated actuators 702 to grasp and carry an object. The appendages 600 a, 600 b could also point downward as shown in FIG. 1D for adjusting the moment of inertia about the vertical z-axis to assist with turning maneuvers. FIG. 1E shows the appendages 600 a, 600 b fully extended/deployed outward from the IPB 200 with each appendage 600 a, 600 b having the corresponding portions 601, 602, 603 substantially aligned with one another and extending substantially parallel to the ground surface 12. In some examples, the robot 100 may fully extend one or both of appendages 600 a, 600 b as shown in FIG. 1E for adjusting the moment of inertia about the vertical z-axis.

Referring back to FIG. 1C, the robot 100 includes a control system 10 configured to monitor and control operation of the robot 100. In some implementations, the robot 100 is configured to operate autonomously and/or semi-autonomously. However, a user may also operate the robot by providing commands/directions to the robot 100. In the example shown, the control system 10 includes a controller 102 (e.g., data processing hardware), memory hardware 104, an inertial measurement unit 106, actuators 108, one or more sensors 110, and one or more power sources 112. The control system 10 is not limited to the components shown, and may include additional or less components without departing from the scope of the present disclosure. The components may communicate via wireless or wired connections and may be distributed across multiple locations of the robot 100. In some configurations, the control system 10 interfaces with a remote computing device and/or a user. For instance, the control system 10 may include various components for communicating with the robot 100, such as a joystick, buttons, wired communication ports, and/or wireless communication ports for receiving inputs from the remote computing device and/or user, and providing feedback to the remote computing device and/or user.

The controller 102 corresponds to data processing hardware that may include one or more general purpose processors, digital signal processors, and/or application specific integrated circuits (ASICs). In some implementations, the controller 102 is a purpose-built embedded device configured to perform specific operations with one or more subsystems of the robot 100. The memory hardware 104 is in communication with the controller 102 and may include one or more non-transitory computer-readable storage media such as volatile and/or non-volatile storage components. For instance, the memory hardware 104 may be associated with one or more physical devices in communication with one another and may include optical, magnetic, organic, or other types of memory or storage. The memory hardware 104 is configured to, inter alia, to store instructions (e.g., computer-readable program instructions), that when executed by the controller 102, cause the controller to perform numerous operations, such as, without limitation, altering the pose P of the robot 100 for maintaining balance, maneuvering the robot 100 across the ground surface 12, transporting objects, and/or executing a sit-to-stand routine. The controller 102 may directly or indirectly interact with the inertial measurement unit 106, the actuators 108, the sensor(s) 110, and the power source(s) 112 for monitoring and controlling operation of the robot 100.

The inertial measurement unit 106 is configured to measure an inertial measurement indicative of a movement of the robot 100 that results in a change to the pose P of the robot 100. The inertial measurement measured by the inertial measurement unit 106 may indicate a translation or shift of the CM of the robot 100 relative to the vertical gravitational axis V_(g). The translation or shift of the CM may occur along one or more of the fore-aft axis (x-axis), the lateral axis (y-axis), or the vertical axis (z-axis). For instance, the inertial measurement unit 106 may detect and measure an acceleration, a tilt, a roll, a pitch, a rotation, or yaw of the robot 100, as the inertial measurement, using an initial pose P as an inertial reference frame. To detect and to measure, the inertial measurement unit 106 may include at least one of a tri-axial accelerometer, a tri-axial magnetometer, or a tri-axial gyroscope. The tri-axial accelerometer includes circuitry to sense the movement of the robot 100 between poses along a straight line or an axis, such as a position and an orientation of the inertial measurement unit 106. In some examples, the accelerometer may use a mass-spring system or a vibration system configured to determine an acceleration corresponding to a displacement of a mass in the mass-spring system or a stress related to a vibration in the vibration system. The inertial measurement unit 106 may also include a gyroscope, such as the tri-axial gyroscope, to measure a rate of rotation about a defined axis. The gyroscope is configured to sense rotation of the inertial measurement unit 106 such that a sensed rotation is a portion of the inertial measurement output to the controller 102. The controller 102 receives the inertial measurement of the inertial measurement unit 106 and determines shifts in the CM of the robot 100 relative to the vertical gravitational axis V_(g). Thus, the gyroscope senses rotations of the robot 100 as the robot 100 moves with the gyroscope. The inertial measurement unit 106 may include more than one of the tri-axial accelerometer, the tri-axial magnetometer, or the tri-axial gyroscope to increase accuracy of the inertial measurement unit 106. In some examples, the inertial measurement unit 106 produces three dimensional measurements of a specific force and an angular rate. The inertial measurement unit 106 may also include a microprocessor.

The controller 102 is configured to process data relating to the inertial measurement unit 106, the actuators 108, and the sensor(s) 110 for operating the robot 100. The controller 102 receives an inertial measurement from the inertial measurement unit 106 (e.g., via a wired or wireless connection) disposed on the robot 100 and instructs actuation of at least one of the actuators 108 to alter a pose P of the robot 100 to move the CM of the robot 100 relative to the vertical gravitational axis V_(g). In some examples, the controller 102 identifies changes in the inertial measurements between poses P and defines movements by at least one of the counter-balance body 300 or the articulated arm 600 for maintaining balance of the robot 100 by moving the CM relative to the vertical gravitational axis V_(g).

The actuators 108 may include the tail actuator 352 connected to the tail 300 (e.g., counter-balance body), the leg actuators 413 each connected to the respective leg 400, the drive motors 510 each coupled to the respective drive wheel 500 of the corresponding leg 400, and the manipulator head actuator 652 connected to the manipulator head 600 (e.g., articulated arm). The tail actuator 352 is configured to move the tail 300 relative to the torso 200. For instance, the controller 102 may instruct actuation of the tail actuator 352 to move/pitch the tail 300 about the lateral axis (y-axis) relative to the torso 200. The manipulator head actuator 652 is configured to move the manipulator head 600 relative to the torso 200. For instance, the controller 102 may instruct actuation of the manipulator head actuator 652 to move/pitch the manipulator head 600 about the lateral axis (y-axis) relative to the torso 200. In some examples, the controller 102 actuates the manipulator head actuator 652 to operate the manipulator head 600 as a second counter-balance body for altering the pose P of the robot 100 by moving the CM of the robot 100 relative to the vertical gravitational axis V_(g). The controller 102 may additionally or alternatively instruct actuation of at least one of the actuator 662 corresponding to the second articulated arm joint (e.g., second manipulator head joint) J1 660 or the actuator 662 corresponding to the third articulated arm joint (e.g., third manipulator head joint) J₂ 670 for moving at least one of the portions 601, 602, 603 of the manipulator head relative to one another and relative to the torso 200.

Each leg actuator 413 (disposed at or near the corresponding hip joint 412) is configured to rotate the upper portion 401 of the respective leg 400 relative to the torso 200. For instance, the controller 102 may instruct actuation of the leg actuator 413 or the belt drive actuator 415 associated with the right hip joint 412 to cause the upper portion 401 of the prismatic right leg 400 a to move/pitch around the lateral axis (y-axis) relative to the tail 200. Similarly, the controller 102 may instruct actuation of the leg actuator 413 associated with the left hip joint 412 to cause the left leg 400 b to move/pitch around the lateral axis (y-axis) relative to the tail 200. In some implementations, the actuators 108 further include the belt drive actuators 415 configured to drive the corresponding belts 417 when actuated by the controller 102. For instance, the controller 102 may instruct actuation of the belt drive actuator 415 in first/second directions to prismatically extend or retract a length of a respective prismatic leg 400 by causing a lower portion 402 of the prismatic leg 400 to rotate about the corresponding knee joint 414 relative to the corresponding upper portion 401. In some configurations, an actuator is disposed at the corresponding knee joint 414 in lieu of the belt drive actuator 415 for moving the lower portion 402 of the leg 400 relative to the upper portion 401.

Each drive motor 510 is configured to apply the corresponding axle torque (FIG. 1B) for rotating the respective drive wheel 500 about the corresponding ankle joint 422 to move the drive wheel 500 across the ground surface 12 along the fore-aft axis (x-axis). For instance, the axle torque T_(a) may cause the drive wheel 500 to rotate in a first direction for moving the robot 100 in a forward direction along the fore-aft axis (x-axis) and/or cause the drive wheel 500 to rotate in an opposite second direction for moving the robot 100 in a rearward direction along the fore-aft axis (x-axis). The controller 102 may instruct actuation of each drive motor 510 via a corresponding axle torque command T_(a) _(_) _(cmd) that specifies a magnitude and direction of axle torque T_(a) for the drive motor 510 to apply for rotating the respective drive wheel 500 in the forward or backward direction. Based on the inertial measurement received from the inertial measurement unit 106, the controller 102 may provide a corresponding axle torque command T_(a) _(_) _(cmd) to at least one of the drive motors 510 to instruct the drive motor 510 to apply the corresponding axle torque T_(a) in order to control tilt to maintain or restore balance of the robot 100.

The sensor(s) 110 of the control system 10 may include, without limitation, one or more of force sensors, torque sensors, velocity sensors, acceleration sensors, position sensors (linear and/or rotational position sensors), motion sensors, location sensors, load sensors, temperature sensors, touch sensors, depth sensors, ultrasonic range sensors, infrared sensors, object sensors, and/or cameras. The sensors 110 may disposed on the robot 100 at various locations such as the torso 200, tail 300, the at least one leg 400, the drive wheel 500, the articulated arm 600, and/or the end effector 700. The sensors 110 are configured to provide corresponding sensor data to the controller 102 for monitoring and controlling operation of the robot 100 within an environment. In some examples, the controller 102 is configured to receive sensor data from sensors physically separated from the robot 100. For instance, the controller 102 may receive sensor data from a proximity sensor disposed on a target object the robot 100 is configured to locate and transport to a new location.

The sensor data from the sensors 110 may allow the controller 102 to evaluate conditions for maneuvering the robot 100, altering a pose P of the robot 100, and/or actuating various actuators 108 for moving/rotating mechanical components such as the counter-balance body 300, the at least one leg 400, the drive wheel 500 rotatably coupled to the at least one leg 400, the articulated arm 600, and the end effector 700. In some examples, the sensor data includes rotational positions of the back joint bk, 350, the hip joint(s) 412, and/or the articulated arm joints J₀ 650, J₁ 660, J₂ 670 used to indicate a state of at least one of the counter-balance body 300, the at least one leg 400, the articulated arm 600, or the end effector 700. In some examples, the robotic system 10 employs one or more force sensors to measure load on the actuators that move the counter-balance body 300, the at least one leg 400, the drive wheel 500 rotatably coupled to the at least one leg 400, the articulated arm 600, or the end effector 700. The sensors 110 may further include position sensors to sense states of extension, retraction, and/or rotation of the counter-balance body 300, the at least one leg 400, the drive wheel 500 rotatably coupled to the at least one leg 400, the articulated arm 600, or the end effector 700.

Other sensors 110 may capture sensor data corresponding to the terrain of the environment and/or nearby objects/obstacles to assist with environment recognition and navigation. For instance, some sensors 110 may include RADAR (e.g., for long-range object detection, distance determination, and/or speed determination) LIDAR (e.g., for short-range object detection, distance determination, and/or speed determination), VICON® (e.g., for motion capture), one or more imaging (e.g., stereoscopic cameras for 3D vision), perception sensors, a global positioning system (GPS) device, and/or other sensors for capturing information of the environment in which the robotic system 100 is operating.

In some implementations, the control system 10 includes one or more power sources 112 configured to power various components of the robot 100. The power sources 112 employed by the robot 100 may include, without limitation, a hydraulic system, an electrical system, energy storage device(s) (e.g. batteries), and/or pneumatic devices. For instance, one or more energy storage devices may provide power to various components (e.g., actuators 108) of the robot 100. The drive motors 510 may include electric motors that receive power from one or more energy storage devices. In some examples, the counter-balance body 300 defines a compartment for storing and retaining energy storage devices. The energy storage devices may be chargeable via wired connections or wireless (e.g. induction) connections to an external power source. Energy storage devices could also be charged using solar energy (e.g., generated via solar panels disposed on the robot 100). In some examples, the energy storage devices are removable so that depleted energy storage devices can be replaced with fully-charged energy storage devices. Gasoline engines could also be employed. A hydraulic system may employ hydraulic motors and cylinders for transmitting pressurized fluid for operating various components of the robot 100.

Banked Turns

Referring to FIGS. 1F-1I, in some implementations, the controller 102 is responsible for maneuvering the robot 100, 100 a in an operating environment. In these implementations, the controller 102 is configured to perform maneuverability operations that include driving the robot 100 across the ground surface 12 and turning the robot 100 by shifting the CM of the robot 100 toward a turning direction 160, thereby leaning the robot 100 into the turning direction 160. As used herein, and described in greater detail below, differential wheel drive causes the turning of the robot 100 while the shifting of the CM of the robot 100 toward the turning direction 160 occurs during the turn in order to assist with stability and maintain balance of the robot 100 during the turn. The turning direction 160 may extend on either side of the fore-aft axis (x-axis) and include a first turning direction associated with a left turn or a right turn, and an opposite left turning direction associated with the other one of the left turn or the right turn.

FIG. 1F shows the robot 100, 100 a traversing across the ground surface 12 along a path 50 that includes straight portions and curved portions. At a first location L1, the robot 100 assumes a corresponding first pose P₁ while driving straight in the forward direction along the fore-aft axis (x-axis). At a second location L₂, the robot 100 assumes a corresponding second pose P₂ while executing a turning maneuver in a turning direction 160. Here, the robot 100 attains the second pose P₂ by shifting the CM of the robot 100 toward the turning direction 160. The shifting of the CM of the robot 100 toward the turning direction 160 may cause the drive wheels 500 of the variable length legs 400 to lean into the turning direction 160. In the example shown, the turning direction 160 corresponds to a left turn. The second pose P₂ of the robot 100 may further include lowering the CM of the robot 100 closer to the ground surface 12 from a position of the CM of the robot 100 at the first position P₁.

FIG. 1G depicts the robot 100 having the second pose P₂ at the second location L₂ of FIG. 1F while executing the turning maneuver in the left turning direction 160 (relative to the forward direction of travel of the robot 100). The controller 102 may effectuate the left turn by instructing the right drive motor 510 a to apply a greater magnitude of axle torque T_(aR) than a magnitude of torque T_(aL) applied by the left drive motor 510 b to cause the right drive wheel 500 a to rotate at a greater rotational velocity than a rotational velocity of the left drive wheel 500 b. Similarly, when executing a turning maneuver to the right, the controller 102 may instruct the left drive motor 510 b to apply a greater magnitude of axle torque T_(aL) than a magnitude of torque T_(aR) applied by the right drive motor 510 a to cause the left drive wheel 500 b to rotate at a greater rotational velocity than a rotational velocity of the right drive wheel 500 a. FIG. 1I shows a top view of a direction of travel D_(T) by the robot 100 while turning in the turning direction 160 at a yaw angle λ relative to the fore-aft axis (x-axis). Here, the direction of travel D_(T) becomes a new fore-aft axis (x-axis) for the robot 100 while the fore-aft axis (x-axis) depicted in the example corresponds to the previous fore-aft axis (x-axis) prior to executing the turning maneuver in the turning direction 160.

Based on the velocity of the robot 100, among other parameters, turning the robot 100 at a turn rate-of-change that is too fast and/or at a yaw angle λ that is too large may cause the CM of the robot 100 to shift away from the turning direction 160 and potentially result in the robot 100 falling over. Accordingly, in order to maintain balance of the robot 100 while executing a turning maneuver, the controller 102 may cause the robot 102 to turn at a turn parameter that satisfies a threshold turn parameter for the turning maneuver. In some examples, the turn parameter includes a turn rate-of-change and the threshold turn parameter may include a threshold turn rate-of-change. Here, the threshold turn rate-of-change may define a maximum turn rate-of-change for maintaining balance during the turn. In other examples, the turn parameter includes a yaw angle λ and the threshold turn parameter includes a threshold yaw angle. The threshold yaw angle may define a maximum yaw angle for maintaining balance of the robot 100 during the turn. In some implementations, turning the robot 102 includes turning the robot 100 at both a yaw angle λ that satisfies a threshold yaw angle for a turn and a turn rate-of-change that satisfies a threshold turn rate-of-change for the turn. The threshold turn rate-of-change and the threshold yaw angle may each depend upon the velocity of the robot 100 when executing the turn. For instance, values for the threshold turn rate-of-change and the threshold yaw angle may reduce at faster robot velocities and increase at slower robot velocities.

In some implementations, the controller 102 causes the counter-balance body 300 (e.g., tail) to move relative to the IPB 200 (e.g., torso) to assist with balancing the robot 100 during turns. More specifically, the controller 102 may actuate the counter-balance body 300 (e.g., via the tail actuator 352) to move/pitch about the lateral axis (y-axis) in a direction toward the ground surface 12, thereby altering the pose P of the robot 100 by lowering the CM of the robot 100 closer to the ground surface 12. Here, the rotational angle θ_(CBB) (FIG. 1B and 1C) of the counter-balance body 300 relative to the vertical gravitational axis V_(g) increases as the counter-balance body 300 moves toward the ground surface 12 relative to the IPB 200.

Referring to FIGS. 1G and 1H, in some implementations, the controller 102 shifts the CM of the robot 100 toward the turning direction 160 by altering a length of the at least one leg 400. For instance, when the turning direction 160 is to the left as shown in FIGS. 1F-1H, the controller 102 may retract the length of the left leg 400 b to reduce a height H1 of the left leg 400 b with respect to the ground surface 12 to a value less than a height H2 of the right leg 400 a with respect to the ground surface 12. The height H1 of the left leg 400 b is defined as a distance along the vertical axis (z-axis) between the ground surface 12 (or the left ankle joint 422 b) and the left hip joint 412 (or the left knee joint 414) that rotatably (prismatically) couples the respective first end 410 b of the left leg 400 b to the second end portion 220 of the IPB 200. Likewise, the corresponding height H2 of the right leg 400 a is defined as a distance along the vertical axis (z-axis) between the ground surface 12 (or the right ankle joint 422 a) and the right hip joint 412 (or the right knee joint 414) that rotatably (prismatically) couples the corresponding first end 410 a of the right leg 400 a to the second end portion 220 of the IPB 200.

In the examples shown, the right and left drive wheels 500 a, 500 b lean into the left turning direction 160 as a result of the left leg 400 b (i.e., the leg 400 on the side of the turning direction 160) having the corresponding height H1 that is less than the corresponding height H2 of the right leg 400 a (i.e., the leg 400 on the opposite side of the turning direction 160). The controller 102 may also retract the length of the right leg 400 a, but to a lesser extent than the left leg 400 b, so long as the height H1 (and length) of the left leg 400 b is less than the height H2 (and length) of the right leg 400 a to enable the robot 100 to lean into the left turning direction 160. Similarly, right turning directions 160 include the controller 102 retracting the length of at least the right leg 400 a to cause the height of the corresponding right leg 400 a to be less than the height of the left leg 400 b, thereby enabling the right and left drive wheels 500 a, 500 b to lean into the right turning direction 160 (not shown) and cause the CM of the robot 100 to shift into the right turning direction 160. When not turning, the CM of the robot 100 is typically centered between the drive wheels 500 a, 500 b.

The altering of the heights H1, H2 of the legs 400 with respect to the ground surface to cause the right and left drive wheels 500 a, 500 b to lean into the turning direction 160 provides the robot 100 with a banked turning capability that enables the robot 100 to maintain momentum, stability, and handle execution of the turning maneuver more efficiently. Thus, the banked turn may aid with execution of the turning maneuver by canceling out a moment caused by centripetal force with a gravity moment due to the shifting of the CM of the robot 100 toward the turning direction 160 while driving across the ground surface 12. Incidentally, the leaning by the robot 100 into the turning direction 160 may also apply gyroscopic effects on the drive wheels 500 that may, to some extent, also assist with effectuating the turning maneuver.

FIG. 1J provides a detailed view of the right and drive wheels 500 a, 500 b of FIG. 1G while leaning into the left turning direction 160. In the example shown, the leaning of the drive wheels 500 a, 500 b causes the robot 100 to lean at a roll angle α that satisfies a threshold roll angle for the robot 100. The roll angle α is measured between the ground surface 12 and a line extending from a point of contact PC centered between the right and left drive wheels 500 a, 500 b on the ground surface 12 and the CM of the robot 100. In configurations where the robot 100 includes a single leg 400 and corresponding drive wheel 500, the roll angle may be measured between the ground surface 12 and a line extending from a point of contact PC between the wheel 500 of the leg 400 and the ground surface 12 and the CM of the robot 100. Here, the term “roll” is used to describe that the robot 100 is “leaning” with respect to the fore-aft axis (x-axis), which generally denotes a roll axis, with the lateral axis (y-axis) and the vertical axis (z-axis) denoting pitch and yaw axes, respectively. In other words, the leaning at the roll angle α by the robot 100 does not include the robot 100 manifestly “rolling” about the fore-aft axis (x-axis), but rather “leaning” with respect to the fore-aft axis (x-axis) to cause the CM of the robot 100 to shift into the turning direction 160 when the roll angle α satisfies a threshold roll angle for the robot 100. The threshold roll angle may include a minimum roll angle required to cause the CM of the robot 100 to shift into the turning direction 160. The threshold roll angle may be based on at least one of a velocity of the robot 100, a turn rate-of-change for the turn, and or the yaw angle λ (FIG. 1I) for the turn.

Referring to FIG. 2, in some implementations, a robot 100 b includes an inverted pendulum body (IPB) 200, a counter-balance body 300 disposed on the IPB 200, at least one leg 400 having a first end 410 and a second end 420, and a drive wheel 500 rotatably coupled to the second end 420 of the at least one leg 400. In view of the substantial similarity in structure and function of the components associated with the robot 100 a with respect to the robot 100 b, like reference numerals are used herein after and in the drawings to identify like components.

As with the robot 100 a of FIGS. 1A-1E, the robot 100 b has a vertical gravitational axis V_(g), which is perpendicular to a ground surface 12 along a direction of gravity, and a center of mass CM, which is a point where the robot 100 has a zero sum distribution of mass. The robot 100 further has a pose P based on the CM relative to the vertical gravitational axis V_(g) to define a particular attitude or stance assumed by the robot 100. The attitude of the robot 100 can be defined by an orientation or an angular position of an object in space.

The IPB 200 includes the first end portion 210 and the second end portion 220. While the counter-balance body 300 of the robot 100 a of FIGS. 1A-1E is disposed on the first end portion 210 of the IPB 200, the counter-balance body 300 of the robot 100 b of FIG. 2 is disposed on the second end portion 220 of the IPB 200. In a similar fashion to the counter-balance body 300 of the robot 100 a, the counter-balance body 300 of the robot 100 b may move/pitch around a lateral axis (y-axis) that extends perpendicular to the gravitational vertical axis V_(g) and a fore-aft axis (x-axis) of the robot 100 for altering a pose P of the robot 100 b. For instance, the counter-balance body 300 may move/pitch relative to the gravitational vertical axis V_(g) in a first direction for shifting the CM of the robot 100 b towards the ground surface 12 and in an opposite second direction for shifting the CM of the robot 100 b away from the ground surface 12. Accordingly, rotational movement by the counter-balance body 300 relative to the IPB 200 may be used for balancing and maintaining the robot 100 b in an upright position.

The at least one leg 400 of the robot 100 b may include the variable length right and left legs 400 a, 400 b each including a corresponding first end 410 rotatably coupled to the second end portion 220 of the IPB 200 and a corresponding second end 420 rotatably coupled to a corresponding right drive wheel 500 a, 500 b. In a similar fashion to the robot 100 a, the robot 100 b may employ various actuators for altering the lengths of the legs 400 a, 400 b. For instance, a length/height of at least one of the legs 400 a, 400 b may be altered lean the drive wheels 500 a, 500 b into a turning direction to assist with a turning maneuver.

With continued reference to FIG. 2, the robot 100 b further includes an articulated arm 600 disposed on the IPB 200 and configured to move relative to the IPB 200. The articulated arm 600 may have five-degrees of freedom. By contrast to the robot 100 a of FIGS. 1A-1E having the articulated arm 600 disposed on the second end portion 220 of the IPB 200, the robot 100 b includes the articulated arm 600 disposed on the first end portion 210 of the IPB 200. The articulated arm 600 extends between a proximal first end 610 rotatably coupled to the IPB 200 and a distal second end 620. In the example shown, the articulated arm 600 includes two portion 601, 602 rotatable relative to one another and also the IPB 200; however, the articulated arm 600 may include more or less portions without departing from the scope of the present disclosure. An end effector 700 may be coupled to the distal second end 620 of the articulated arm 600 and may include one or more actuators 702 for gripping/grasping objects. The end effector 700 may optionally include one or more suction cups 704 configured to provide a vacuum seal between the end effector 700 and a target object to allow the articulated arm 600 to carry the target object.

Referring to FIG. 3, in some implementations, a robot 100 c includes an inverted pendulum body (IPB) 200, a counter-balance body 300 disposed on the IPB 200, at least one leg 400 having a first end 410 and a second end 420, and a drive wheel 500 rotatably coupled to the second end 420 of the at least one leg 400. In view of the substantial similarity in structure and function of the components associated with the robot 100 a with respect to the robot 100 b, like reference numerals are used herein after and in the drawings to identify like components.

As with the robot 100 a of FIGS. 1A-1E, the robot 100 c has a vertical gravitational axis V_(g), which is perpendicular to a ground surface 12 along a direction of gravity, and a center of mass CM, which is a point where the robot 100 has a zero sum distribution of mass. The robot 100 further has a pose P based on the CM relative to the vertical gravitational axis V_(g) to define a particular attitude or stance assumed by the robot 100 c. The attitude of the robot 100 can be defined by an orientation or an angular position of an object in space.

The IPB 200 includes the first end portion 210 and the second end portion 220. While the counter-balance body 300 of the robot 100 a of FIGS. 1A-1E is disposed on the first end portion 210 of the IPB 200, the counter-balance body 300 of the robot 100 c of FIG. 3 is disposed on the second end portion 220 of the IPB 200. In a similar fashion to the counter-balance body 300 of the robot 100 a, the counter-balance body 300 of the robot 100 b may move/pitch around a lateral axis (y-axis) that extends perpendicular to the gravitational vertical axis V_(g) and a fore-aft axis (x-axis) of the robot 100 c for altering a pose P of the robot 100 c. For instance, the counter-balance body 300 may move/pitch relative to the gravitational vertical axis V_(g) in a first direction for shifting the CM of the robot 100 b towards the ground surface 12 and in an opposite second direction for shifting the CM of the robot 100 c away from the ground surface 12. Accordingly, rotational movement by the counter-balance body 300 relative to the IPB 200 may be used for balancing and maintaining the robot 100 c in an upright position.

The at least one leg 400 of the robot 100 c may include the variable length right and left legs 400 a, 400 b each including a corresponding first end 410 rotatably coupled to the second end portion 220 of the IPB 200 and a corresponding second end 420 rotatably coupled to a corresponding right drive wheel 500 a, 500 b. In a similar fashion to the robot 100 a, the robot 100 c may employ various actuators for altering the lengths of the legs 400 a, 400 b. For instance, a length/height of at least one of the legs 400 a, 400 b may be altered lean the drive wheels 500 a, 500 b into a turning direction to assist with a turning maneuver.

With continued reference to FIG. 3, the robot 100 c further includes an articulated arm 600 disposed on the IPB 200 and configured to move relative to the IPB 200. The articulated arm 600 may have five-degrees of freedom. By contrast to the robot 100 c of FIGS. 1A-1E having the articulated arm 600 disposed on the second end portion 220 of the IPB 200, the robot 100 b includes the articulated arm 600 disposed on the first end portion 210 of the IPB 200. The articulated arm 600 extends between a proximal first end 610 rotatably coupled to the IPB 200 and a distal second end 620. In the example shown, the articulated arm 600 includes two portion 601, 602 rotatable relative to one another and also the IPB 200; however, the articulated arm 600 may include more or less portions without departing from the scope of the present disclosure. An end effector 700 may be coupled to the distal second end 620 of the articulated arm 600 and may include one or more actuators 702 for gripping/grasping objects. The end effector 700 may optionally include one or more suction cups 704 configured to provide a vacuum seal between the end effector 700 and a target object to allow the articulated arm 600 to carry the target object.

FIG. 4 illustrates a method 1400 for operating a robot 100. At block 1402, the method 1400 includes driving the robot 100 across a surface 12. The robot 100 includes an inverted pendulum body (IPB) 200 having first and second end portions 210, 220 and defining a forward driving direction (e.g., along the fore-aft axis (x-axis)). The robot further includes a counter-balance body 300 and at least one leg 400 having first and second ends 410, 420. The counter-balance body 300 is disposed on the IPB 200 and configured to move relative to the IPB 200, while the first end 410 of the at least one leg 400 is rotatably coupled to the second end portion 220 of the IPB 200. The counter-balance body 300 may be disposed on the first end portion 220 of the IPB 200 as shown in FIGS. 1A-1J or the second end portion 210 of the IPB 200 as shown in FIGS. 2 and 3. The robot 100 further includes a drive wheel 500 rotatably coupled to the second end 420 of the at least one leg 400.

At block 1404, the method 1400 also includes turning the robot 100 by shifting a center of mass CM of the robot 100 toward a turning direction 160. The shifting of the CM of the robot 100 toward the turning direction 160 causes the robot 100 to lean into the turning direction. In some examples, at block 1406, the method 400 shifts the CM of the robot 100 toward the turning direction 160 by moving the counter-balance body 300 relative to the IPB 200. For instance, the counter-balance body 300 may move/pitch about a lateral axis (y-axis) relative to the IPB 200 to alter a pose P of the robot 100 by lowering the CM of the robot 100 closer to the ground surface 12.

Additionally or alternatively, the method 1400 may shift the CM of the robot 100 toward the turning direction 160 by altering a height of the at least one leg 400 with respect to the ground surface 12. For instance, the at least one leg 400 may include a right leg 400 a and a left leg 400 b each having a respective upper portion 401 and a respective lower portion 402. Altering the height of the at least one leg 400 may include retracting a length of at least one of the legs 400 a, 400 b so that a height of the leg 400 a, 400 b on a side of the turning direction 400 is less than a height of the other leg 400 a, 400 b on an opposite side of the turning direction 400, thereby causing the wheels 500 a, 500 a rotatably coupled to the corresponding legs 400 a, 400 b to lean into the turning direction 160 to assist with the turn.

In some examples, turning the robot 100 includes turning the robot 100 at a turn parameter that satisfies a threshold turn parameter for a turn. For instance, the turn parameter may include a turn rate-of-change satisfying a threshold turn rate-of-change for the turn and/or a yaw angle λ (FIG. 11) satisfying a threshold yaw angle for the turn. Additionally or alternatively, turning the robot 100 may optionally include leaning the robot 100 at a roll angle α that satisfies a threshold roll angle for the robot 100. With reference to FIG. 2J, the roll angle α may be measured between the ground surface 12 and a line extending from a point of contact PC between the wheel 500 of the at least one leg 400 and the ground surface 12 and the CM of the robot 100. When the robot 100 includes two legs, the point of contact PC may be centered between the right and left drive wheels 500 a, 500 b on the ground surface 12.

The robot 100 may further include one or more articulated arms 600, 600 a, 600 b disposed on the IPB 200 and movable relative to the IPB 200. For instance, the one or more articulated arms 600 may be disposed on second end portion 220 of the IPB 200 when the counter-balance body 300 is disposed on the first end portion 210 of the IPB 200. Alternatively, the one or more articulated arms 600 may be disposed on the first end portion 220 of the IPB 200 when the counter-balance body 300 is disposed on the second end portion of the IPB 200. The robot 100 may actuate the articulated arm(s) 600 to assist with balancing the robot 100 during turning maneuvers and/or in other scenarios.

A software application (i.e., a software resource) may refer to computer software that causes a computing device to perform a task. In some examples, a software application may be referred to as an “application,” an “app,” or a “program.” Example applications include, but are not limited to, system diagnostic applications, system management applications, system maintenance applications, word processing applications, spreadsheet applications, messaging applications, media streaming applications, social networking applications, and gaming applications.

The non-transitory memory may be physical devices used to store programs (e.g., sequences of instructions) or data (e.g., program state information) on a temporary or permanent basis for use by a computing device. The non-transitory memory may be volatile and/or non-volatile addressable semiconductor memory. Examples of non-volatile memory include, but are not limited to, flash memory and read-only memory (ROM)/programmable read-only memory (PROM)/erasable programmable read-only memory (EPROM)/electronically erasable programmable read-only memory (EEPROM) (e.g., typically used for firmware, such as boot programs). Examples of volatile memory include, but are not limited to, random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), phase change memory (PCM) as well as disks or tapes.

FIG. 5 is schematic view of an example computing device 1500 that may be used to implement the systems and methods described in this document. The computing device 1500 is intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. The components shown here, their connections and relationships, and their functions, are meant to be exemplary only, and are not meant to limit implementations of the inventions described and/or claimed in this document.

The computing device 1500 includes a processor 1510, memory 1520, a storage device 1530, a high-speed interface/controller 1540 connecting to the memory 1520 and high-speed expansion ports 1550, and a low speed interface/controller 560 connecting to a low speed bus 1570 and a storage device 1530. Each of the components 1510, 1520, 1530, 1540, 1550, and 1560, are interconnected using various busses, and may be mounted on a common motherboard or in other manners as appropriate. The processor 1510 can process instructions for execution within the computing device 1500, including instructions stored in the memory 1520 or on the storage device 1530 to display graphical information for a graphical user interface (GUI) on an external input/output device, such as display 1580 coupled to high speed interface 1540. In other implementations, multiple processors and/or multiple buses may be used, as appropriate, along with multiple memories and types of memory. Also, multiple computing devices 500 may be connected, with each device providing portions of the necessary operations (e.g., as a server bank, a group of blade servers, or a multi-processor system).

The memory 1520 stores information non-transitorily within the computing device 500. The memory 1520 may be a computer-readable medium, a volatile memory unit(s), or non-volatile memory unit(s). The non-transitory memory 1520 may be physical devices used to store programs (e.g., sequences of instructions) or data (e.g., program state information) on a temporary or permanent basis for use by the computing device 1500. Examples of non-volatile memory include, but are not limited to, flash memory and read-only memory (ROM)/programmable read-only memory (PROM)/erasable programmable read-only memory (EPROM)/electronically erasable programmable read-only memory (EEPROM) (e.g., typically used for firmware, such as boot programs). Examples of volatile memory include, but are not limited to, random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), phase change memory (PCM) as well as disks or tapes.

The storage device 1530 is capable of providing mass storage for the computing device 1500. In some implementations, the storage device 1530 is a computer-readable medium. In various different implementations, the storage device 1530 may be a floppy disk device, a hard disk device, an optical disk device, or a tape device, a flash memory or other similar solid state memory device, or an array of devices, including devices in a storage area network or other configurations. In additional implementations, a computer program product is tangibly embodied in an information carrier. The computer program product contains instructions that, when executed, perform one or more methods, such as those described above. The information carrier is a computer- or machine-readable medium, such as the memory 1520, the storage device 1530, or memory on processor 1510.

The high speed controller 1540 manages bandwidth-intensive operations for the computing device 1500, while the low speed controller 1560 manages lower bandwidth-intensive operations. Such allocation of duties is exemplary only. In some implementations, the high-speed controller 1540 is coupled to the memory 1520, the display 1580 (e.g., through a graphics processor or accelerator), and to the high-speed expansion ports 1550, which may accept various expansion cards (not shown). In some implementations, the low-speed controller 1560 is coupled to the storage device 1530 and a low-speed expansion port 1590. The low-speed expansion port 1590, which may include various communication ports (e.g., USB, Bluetooth, Ethernet, wireless Ethernet), may be coupled to one or more input/output devices, such as a keyboard, a pointing device, a scanner, or a networking device such as a switch or router, e.g., through a network adapter.

The computing device 1500 may be implemented in a number of different forms, as shown in the figure. For example, it may be implemented as a standard server 1500 a or multiple times in a group of such servers 1500 a, as a laptop computer 1500 b, or as part of a rack server system 1500 c.

Various implementations of the systems and techniques described herein can be realized in digital electronic and/or optical circuitry, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and/or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device.

These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and can be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As used herein, the terms “machine-readable medium” and “computer-readable medium” refer to any computer program product, non-transitory computer readable medium, apparatus and/or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term “machine-readable signal” refers to any signal used to provide machine instructions and/or data to a programmable processor.

The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

To provide for interaction with a user, one or more aspects of the disclosure can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube), LCD (liquid crystal display) monitor, or touch screen for displaying information to the user and optionally a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. In addition, a computer can interact with a user by sending documents to and receiving documents from a device that is used by the user; for example, by sending web pages to a web browser on a user's client device in response to requests received from the web browser.

A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims. 

What is claimed is:
 1. A method of maneuvering a robot, the method comprising: driving the robot across a surface, the robot comprising: an inverted pendulum body having first and second end portions and defining a forward drive direction; a counter-balance body disposed on the inverted pendulum body and configured to move relative to the inverted pendulum body; at least one leg having first and second ends, the first end of the at least one leg prismatically coupled to the second end portion of the inverted pendulum body; and a drive wheel rotatably coupled to the second end of the at least one leg; and turning the robot by shifting a center of mass of the robot toward a turning direction, thereby leaning the robot into the turning direction, by at least one of: moving the counter-balance body relative to the inverted pendulum body; or altering a height of the at least one leg with respect to the surface.
 2. The method of claim 1, wherein shifting the center of mass of the robot toward the turning direction causes the drive wheel of the at least one leg to lean into the turning direction.
 3. The method of claim 1, wherein the at least one leg comprises: a right leg having first and second ends, the first end of the right leg prismatically coupled to the second end potion of the inverted pendulum body, the right leg having a right drive wheel rotatably coupled to the second end of the right leg; and a left leg having first and second ends, the first end of the left leg prismatically coupled to the second end potion of the inverted pendulum body, the left leg having a left drive wheel rotatably coupled to the second end of the left leg, wherein altering the height of the at least one leg comprises altering the height of at least one of the right leg or the left leg of the robot with respect to the surface, causing the right and left drive wheels to lean into the turning direction.
 4. The method of claim 1, wherein turning the robot further comprises at least one of: turning the robot at a turn parameter that satisfies a threshold turn parameter for a turn; or leaning the robot at a roll angle that satisfies a threshold roll angle of the robot, the roll angle measured between the surface and a line extending from a point of contact between the wheel of the at least one leg and the surface and the center of mass of the robot.
 5. The method of claim 4, wherein the turn parameter comprises a turn rate-of-change and the threshold turn parameter comprises a threshold turn rate-of-change.
 6. The method of claim 4, wherein the turn parameter comprises a yaw angle and the threshold turn parameter comprises a threshold yaw angle.
 7. The method of claim 1, wherein the robot further comprises at least one arm disposed on the inverted pendulum body and configured to move relative to the inverted pendulum body.
 8. The method of claim 7, wherein the at least one arm is rotatably coupled to the first end portion of the inverted pendulum body.
 9. The method of claim 7, wherein the at least one arm is rotatably coupled to the second end portion of the inverted pendulum body.
 10. The method of claim 1, wherein the counter-balance body is rotatably coupled to the first end portion of the inverted pendulum body.
 11. The method of claim 1, wherein the counter-balance body is rotatably coupled to the second end portion of the inverted pendulum body.
 12. A robot comprising: an inverted pendulum body having first and second end portions; a counter-balance body disposed on the inverted pendulum body and configured to move relative to the inverted pendulum body; at least one leg having first and second ends, the first end of the at least one leg prismatically coupled to the second end portion of the inverted pendulum body, the at least one leg having a variable length between the first and second ends; a drive wheel rotatably coupled to the second end of the at least one leg; and a controller in communication with the counter-balance body, the at least one leg, and the drive wheel, the controller configured to perform operations comprising: driving, by the drive wheel, the robot across a surface; and turning the robot by shifting a center of mass of the robot toward a turning direction, thereby leaning the robot into the turning direction, by at least one of: moving the counter-balance body relative to the inverted pendulum body; or altering the length of the at least one leg.
 13. The robot of claim 12, wherein shifting the center of mass of the robot toward the turning direction causes the drive wheel of the at least one leg to lean into the turning direction.
 14. The robot of claim 12, wherein the at least one leg comprises: a right leg having first and second ends, the first end of the right leg prismatically coupled to the second end potion of the inverted pendulum body, the right leg having a right drive wheel rotatably coupled to the second end of the right leg; and a left leg having first and second ends, the first end of the left leg prismatically coupled to the second end potion of the inverted pendulum body, the left leg having a left drive wheel rotatably coupled to the second end of the left leg, wherein altering the length of the at least one leg comprises altering the length of at least one of the right leg or the left leg of the robot, causing the right and left drive wheels to lean into the turning direction.
 15. The robot of claim 12, wherein turning the robot further comprises at least one of: turning the robot at a turn parameter that satisfies a threshold turn parameter for a turn; or leaning the robot at a roll angle that satisfies a threshold roll angle of the robot, the roll angle measured between the surface and a line extending from a point of contact between the wheel of the at least one leg and the surface and the center of mass of the robot.
 16. The robot of claim 15, wherein the turn parameter comprises a turn rate-of-change and the threshold turn parameter comprises a threshold turn rate-of-change.
 17. The robot of claim 15, wherein the turn parameter comprises a yaw angle and the threshold turn parameter comprises a threshold yaw angle.
 18. The robot of claim 12, further comprising at least one arm disposed on the inverted pendulum body and configured to move relative to the inverted pendulum body.
 19. The robot of claim 18, wherein the at least one arm is rotatably coupled to the first end portion of the inverted pendulum body.
 20. The robot of claim 18, wherein the at least one arm is rotatably coupled to the second end portion of the inverted pendulum body.
 21. The robot of claim 12, wherein the counter-balance body is rotatably coupled to the first end portion of the inverted pendulum body.
 22. The robot of claim 12, wherein the counter-balance body is rotatably coupled to the second end portion of the inverted pendulum body. 